The Airtightness Test


It’s always an exciting moment when we test the airtightness of a new home. All the time and expertise OakenStone invest in the design and construction to achieve a super-efficient home is finally put to the test.

Of course, in old houses draughts (the exchange of stale air for fresh) are essential, otherwise homeowners would soon be living in a stale, damp and mouldy environment – unpleasant and unhealthy!

However, as part of our drive to build ever more environmentally sensitive homes, OakenStone use MVHR technology to control the exchange of air, thus retaining and redirecting recovered heat and expelling moisture and odours. For MVHR to work efficiently the shell of the building needs to be as airtight as possible. And if we get it right then the homeowner can look forward to significantly lower heating costs.

So how do we test for airtightness?

All the windows and doors are closed, and all drain points sealed before a large ‘Blower Door’ fan begins to extract air from the building. Highly accurate sensors measure how quickly the extracted air is being replaced (through gaps in the building’s envelope). The quicker air is replaced the leakier the house. However, if the building is close to airtight then the air leaks back in at a much slower rate. This rate is measured by the testing equipment and the reading gives the building its ‘score’.

How did we do?

To give you an idea of the numbers – for a successful test to be registered the score must be below 50 (that would be a very draughty house!).

A standard new build home from a big house builder would normally score in the range of 6-8.

Our most recent airtightness score, for the super-efficient family home we’ve almost completed in Derbyshire Dales was 1.2 – the lowest score we’ve yet achieved!

Oriented and designed with lots of ‘thermal mass’ to capture and store warmth from the sun, and with superior build quality and very high levels of insulation, this new home will require little or no additional heating all year round. A proud achievement for the entire OakenStone team!

Visit our website to find out more about how OakenStone can design and build your new low carbon, super-efficient home, and get rid of draughts once and for all!

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